Interlayer Bound Wannier Excitons in Germanium Sulfide.
Sara Postorino1, Jianbo Sun2, Saskia Fiedler3
1Dipartimento di Fisica, Università degli studi di Roma "Tor Vergata", via della Ricerca Scientifica 1, 00133 Roma, Italy.
Materials (Basel, Switzerland)
|August 19, 2020
Summary
This study investigates germanium sulfide (GeS) using cathodoluminescence, revealing a distinct emission peak. The findings attribute this peak to exciton recombination, highlighting GeS
Area of Science:
- Materials Science
- Condensed Matter Physics
- Optoelectronics
Background:
- Layered germanium sulfide (GeS) exhibits visible light emission and significant anisotropy.
- Recent interest in GeS stems from its unique optoelectronic properties.
Purpose of the Study:
- To investigate the origin of the sharp emission peak observed in GeS.
- To elucidate the role of excitonic recombination and optical anisotropy in GeS.
Main Methods:
- Cathodoluminescence (CL) spectroscopy was performed on GeS flakes.
- Ab initio ground- and excited-state simulations were conducted for bulk GeS.
Main Results:
- A sharp emission peak at ~1.69 eV was observed in GeS flakes, independent of quantum confinement.
- Simulations identified the peak with radiative recombination of the first free bright bound exciton.
- The exciton exhibits a large optical anisotropy and a Wannier-Mott interlayer character.
Conclusions:
- The observed optical emission in GeS is unambiguously explained by exciton recombination.
- GeS demonstrates significant optical anisotropy due to the nature of its excitonic states.
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